From the reaction of 2-acetylcyclopentanone and 2-acetyl-2-methylcyclopentanone with benzohydrazide, the 1-benzoyl-6a-hydroxycyclopentapyrazole derivatives 2a and 2b were obtained as the only reaction products, whereas from the reaction of 2-acetylcyclohexanone an epimeric cis/trans mixture of the 2-benzoyl-3-hydroxy-2H-indazole derivative 3c was formed. The dehydration of the isolated compounds 2a and 3c, as well as the NaBH 4 and NaBH 3 CN reduction products of 2a were studied. The structural assignments of the compounds derived were established by analysis of their NMR spectra ( 1 H,
13C, DEPT, COSY, NOESY, HETCOR CÀH, and COLOC CÀH). The chemoselectivity of the reactions of 1a and 1c with benzohydrazide was studied by conformational analysis with MM2 and semiempirical (AM1 and PM3) MO calculations.